This invention relates to wireless communications, and more specifically to using a single radio to communicate from a remote mobile asset as it passes through a plurality of wireless data networks.
Existing wide area network, that is to say cellular, radios are usually designed and configured to operate with a specific wireless data network. Thus, when a user travels outside of the coverage area of its chosen wireless data network, its radio ceases to function. Some wireless data networks have established cooperative roaming agreements which allow a travelling user with a compatible radio design to operate on a second, foreign wireless data network. Roaming agreements help to alleviate coverage limitations but cannot provide for seamless, global operation due to the existence of wireless data network incompatibilities. Current wide area wireless voice and data networks communicate using different technologies, such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Global System for Mobilization (GSM), Cellular Digital Packet Data (CDPD), DataTac, Mobitex, and General Packet Radios Service (GPRS). The utilization of various frequency bands also segregates wireless networks. While portable radio devices have emerged offering operation on multiple frequency bands, few commercial devices have been realized offering multiple communication modes based upon the different technologies listed above. Thus, when a user enters a region serviced by a non-compatible wireless data network, the user may need to either rent or purchase a radio that is compatible with that region's local network.
A mobile asset, like an individual, may also travel outside of its selected wireless data network. However, it may not be physically or economically possible to install a new, compatible radio device in a mobile asset such as a truck or locomotive. Furthermore, some mobile assets such as railcars, trailers and containers, are typically unattended while in transit. Mobile remote assets would benefit from a suite of radios employing different radio communication technology and, thus, affording communication redundancy in the event that any single radio is outside of its network coverage region. A remote asset with such a suite of differing radios would also benefit from the ability to select that radio and associated wireless data network with appropriate data transfer characteristics (speed, latency) and lowest service costs for the exchange of data. The cost of a redundant radio suite typically prohibits its utility as it includes the parallel hardware as well as recurring service costs associated with the underlying wireless data networks.
A fleet of mobile remote assets would benefit from a radio that is configured to allow each individual mobile asset to communicate with a central service facility regardless of where each respective mobile asset is located and regardless of which wireless data network is available for each respective geographic location.
To address these problems, software defined radio technology is being developed. Software defined radio is an emerging technology, thought to build flexible radio systems with multi-serviced, multi-standard, multi-band operation via re-configurable and re-programmable software instructions. The flexibility of a software defined radio derives from the ability to operate in a multi-serviced environment without being constrained to a particular standard but able to offer, in theory, services in an already standardized or future system, on any radio frequency band. It is believed that U.S. Pat. No. 6,052,600 discloses a software defined radio which must communicate with a base station to receive valid operation licenses and appropriate software configuration instructions in order for the radio to communicate over a plurality of wireless data networks. However, if a system is unable to obtain this information from a base station prior to losing a current wireless data network connection, the radio is not able to dynamically select a new software configuration and wireless data network without directions from the base station.